This application claims the benefit of Korean Patent Application No. 2001-37071, filed on Jun. 27, 2001, under 35 U.S.C. xc2xa7119, the entirety of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an ion implanting system, and more particularly, to a vacuum pump for an ion implanting system.
2. Description of Related Art
An ion implanting system includes a source chamber, an ion beam chamber, a main chamber, and a load lock chamber. Theses chambers include at least one vacuum pump for creating a vacuum atmosphere therein, respectively.
A conventional ion implanting system includes at least one cryo pump, usable as a vacuum pump, for creating a vacuum atmosphere in a main chamber and at least one cryo pump for creating a vacuum atmosphere in the load lock chamber. Further, the at least one cryo pump for creating a vacuum atmosphere in the load lock chamber is usually smaller in size and operated at higher revolutions per minute (rpm) than the at least one cryo pump for creating a vacuum atmosphere in the main chamber. Hence, the cryo pump(s) for creating a vacuum atmosphere in the load lock chamber is contaminated with impurities more easily than the cryo pump(s) for creating a vacuum atmosphere in the main chamber.
A cryo pump creates a vacuum atmosphere in a chamber by condensing and removing gas molecules that contact a cooling portion refrigerated by liquid hydrogen or liquid helium. When an inside of the cryo pump becomes saturated so that an inside temperature of the cryo pump rises, the cryo pump exhausts impurities therein during a regeneration operation. The regeneration operation includes inputting high temperature nitrogen gas into the cryo pump to vaporize the condensed impurities and outwardly exhaust the vaporized impurities.
In other words, when a cryo pump is contaminated with the impurities, an inside temperature of the cryo pump rises. When the inside temperature exceeds a set temperature, an error state is indicated, whereby an operation of the cryo pump is stopped. In order to clean an inside of the cryo pump, an operator initiates a regeneration operation.
Since the cryo pump for creating a vacuum atmosphere in the load lock chamber is contaminated with impurities more easily than the cryo pump for creating a vacuum atmosphere in the main chamber, the cryo pump for creating a vacuum atmosphere in the load lock chamber requires more frequent regeneration operations.
FIG. 1 is a block diagram illustrating a conventional ion implanting system. The ion implanting system of FIG. 1 includes a source chamber 10, an ion beam chamber 12, a main chamber 14, load lock chambers 16-1 to 16-3, a cryo pump controller 18, a compressor 20, a roughing pump 22, cryo pumps 24 to 32, and valves V1 to V14.
The source chamber 10 ionizes gas molecules externally injected. The ion beam chamber 12 accelerates ions input from the source chamber 10 to generate an ion beam. The main chamber 14 irradiates the ion beam from the ion beam chamber 12 into a semiconductor wafer (not shown). The load lock chambers 16-1 to 16-3 load/unload the semiconductor wafer into/from the main chamber 14. The cryo pumps 24 to 30 create a high vacuum atmosphere in the main chamber 14. The cryo pump 32 creates a high vacuum atmosphere in the load lock chambers 16-1 to 16-3 and vacuum lines VL2 to VL5. The valve V5 opens or closes a channel between the source chamber 10 and the ion beam chamber 12. The valve V6 opens or closes a channel between the ion beam chamber 12 and the main chamber 14. The valves V1 to V4 open or close channels between the main chamber 14 and the cryo pumps 24 to 30, respectively. The valves V7 to V9 open or close channels between the main chamber 14 and the load lock chambers 16-1 to 16-3, respectively. The value V10 opens or closes a channel between the cryo pump 32 and the vacuum line VL2. The cryo pump controller 18 applies control signals for controlling the cryo pumps 24 to 32, respectively, and generates an error signal in response to temperature sensing signals xe2x80x9caxe2x80x9d to xe2x80x9cexe2x80x9d, respectively, applied from the cryo pumps when a temperature within the cryo pumps 24 to 32 exceeds a set temperature. The compressor 20 generates control voltages STARTA and RUNA to the cryo pumps 24 to 32 in response to the control signals applied from the cryo pump controller 18. STARTA and RUNA are shown in FIG. 1 as the control voltages for controlling the cryo pump 32.
A vacuum pumping operation of the ion implanting system of FIG. 1 is described below.
Semiconductor wafers (not shown) are loaded into cassettes (not shown) of the load lock chambers 16-1 to 16-3. The valves V11 to V14 are opened, and the valve V10 is closed. A low vacuum atmosphere is created in the load lock chambers 16-1 to 16-3 and the vacuum lines VL1 to VL5 by the roughing pump 22. The roughing pump 22 performs a pumping operation to maintain a pressure of about 10xe2x88x922 torr.
The valve V11 is closed, and the valves V10 and V12 to V14 are opened. A high vacuum atmosphere is created in the load lock chambers 16-1 to 16-3 and the vacuum lines VL2 to VL5 by the cryo pump 32. A high vacuum atmosphere is created such that compressed helium gas from the compressor 20 into the cryo pump 32 reduces a temperature of a gas to be refrigerated. The roughing pump 22 performs a pumping operation to maintain to a pressure of about 10xe2x88x926 torr to about 10xe2x88x925 torr. The cryo pump 32 performs a pumping operation to create a high vacuum atmosphere in the load lock chambers 16-1 to 16-3 and the vacuum lines VL2 to VL5 when the compressor 20 applies the control voltages STARTA and RUNA to the cryo pump 32 in response to the control signal applied from the cryo pump controller 18.
The valves V7 to V9 arranged between the main chamber 14 and the load lock chambers 16-1 to 16-3 are opened, and the cassettes of the load lock chambers 16-1 to 16-3 that load the semiconductor wafers are placed into the main chamber 14. Thereafter, an ion implanting process is performed.
However, since the cryo pump 32 for creating a vacuum in the load lock chambers 16-1 to 16-3 is smaller in size and operates at higher revolutions per minute (rpm) than the cryo pumps 24 to 30 for creating a vacuum in the main chamber 14, the cryo pump 32 is more easily contaminated than the cryo pumps 24 to 30.
A temperature sensing diode (not shown) detects whether the cryo pump 32 is contaminated or not. The cryo pump controller 18 receives a temperature sensing signal xe2x80x9caxe2x80x9d output from the cryo pump 32 and indicates an error state when a temperature inside the cryo pump 32 exceeds a set temperature, thereby stopping an operation of the ion implanting system. The cryo pump 32 performs a regeneration operation to remove the impurities therein and normal operation may continue.
The regeneration operation is performed as follows: nitrogen (N2) gas is input to the cryo pump 32, and therefore an inside pressure of the cryo pump 32 rises and reaches a set pressure of an attached relief valve (not shown). The relief valve is opened to outwardly exhaust the impurities and the nitrogen gas inside the cryo pump 32.
As a result, in the conventional ion implanting system, when the inside temperature of the cryo pump 32 exceeds a set temperature, an error occurs, whereupon a regeneration operation should be performed after stopping the ion implanting system. Also, the ion implanting process cannot be continued until the regeneration operation is completed.
As described above, in a conventional ion implanting system, a cryo pump for creating a vacuum atmosphere in the load lock chamber is easily contaminated, and a regeneration operation should be performed often, which lowers the operational performance of the conventional ion implanting system.
To overcome the problems described above, exemplary embodiments of the present invention describe an ion implanting system having higher operational performance.
At least one exemplary embodiment of the present invention provide an ion implanting system, including an ion implanting chamber for implanting an ion into a semiconductor wafer; a load lock chamber for loading the semiconductor wafer into the ion implanting chamber; a turbo pump for creating a high vacuum atmosphere in the load lock chamber; a low vacuum pump for creating a low vacuum atmosphere in the turbo pump; a cryo pump controller for generating a control signal to control a pumping operation of the turbo pump; a control voltage generator for generating a control voltage in response to the control signal generated from the cryo pump controller; an interface for generating a starting signal in response to the control voltage; and a turbo pump controller for applying a voltage to operate the turbo pump and the low vacuum pump in response to the starting signal output from the interface.
The control voltage generator may be a compressor. The interface may include at least two converters, the first converter converting the control voltage into a digital signal to generate the starting signal, the second converter converting a normal operation sensing signal output from the turbo pump controller into an analog signal to generate a temperature sensing output signal. The first converter may include a first relay operating in response to the control voltage, and a first switch turning on, when the first relay is operated, to generate the starting signal. The second converter may include a second relay operating in response to the normal operation sensing signal, and a current converting circuit for converting a current of the temperature sensing output signal when the second relay is operated.
The current converting circuit may include two diodes serially connected and generate the temperature sensing output signal, and a second switch connected between the two diodes, the second switch connecting both of the two diodes when the second relay is not operated and connecting either of the two diodes when the second relay is operated. The interface may further include an overload sensor for applying the voltage to the low vacuum pump in response to the control voltage and for cutting off the voltage when an overload of the low vacuum pump is sensed. The overload sensor may include a third switch for applying the voltage to the low vacuum pump in response to the control voltage, and a third relay for applying the voltage transferred from the third switch to the low vacuum pump and for cutting off the voltage when an overload of the low vacuum voltage is sensed. The turbo pump controller may include a starter for applying the voltage to the turbo pump in response to a signal applied from the first converter, and a normal operation sensor for receiving a signal applied from the turbo pump to sense a normal operation of the turbo pump in order to generate the normal operation sensing signal.